03 Feb Should Colon Cancer Screening Begin Before 50?
MedicalResearch.com Interview with:
Jordan J. Karlitz, MD
Staff Gastroenterologist Southeast Louisiana Veterans Health Care System
Associate Professor, Division of Gastroenterology
Director, GI Hereditary Cancer and Genetics Program,
Tulane University School of Medicine
MedicalResearch.com: What is the background for this study?
Response: Currently, there is debate over whether average-risk colorectal cancer screening should begin at age 45 or 50.
Given this controversy, we sought to conduct a colorectal cancer incidence rate analysis by yearly-age, as opposed to age range blocks (i.e. 30-39, 40-49 etc.) as has been done in the past. We believed that this type of “high definition” analysis would allow a better understanding of incidence rates of those approaching or at screening in age. We were particularly interested in the transition from age 49 to 50 as this is when average risk screening has historically been recommended.
MedicalResearch.com: What are the main findings?
Response: Our analysis revealed a 46% spike in colorectal cancer incidence rates from age 49 to 50. Many of the lesions accounted for in this incidence rate increase were invasive (beyond in situ stage). Given that tumor growth rates may be several years, these cancers were likely present, yet undetected, while patients were in their 40’s until they were ultimately diagnosed with screening at age 50. This supports the presence of a significant undetected preclinical colorectal cancer burden in those under age 50 which is not reflected in observed SEER incidence rates and that relying on observed incidence rates of those 45-49 years of age alone to assess potential impacts of earlier screening may underestimate cancer prevention benefits. Similar steep incidence rate increases were seen in both men and women, white and black populations and throughout different U.S. regions.
MedicalResearch.com: What should readers take away from your report?
Response: Comparing observed incidence rates between those under age 50 and those 50 years of age or older with regard to estimating the potential impact of earlier screening initiation can be misleading. This is because observed incidence rates in those age 50 and older reflect both average-risk screening detected cases in addition to diagnostically detected cases (due to symptoms) whereas in general, for those under age 50, incidence rates would be expected to primarily reflect only diagnostically detected cases or higher risk screened groups (cancer family history) because average-risk screening has historically not been performed in those under age 50. Observed incidence rates of those in their mid to late 40’s would be expected to be significantly lower than those in their early 50’s, not because the underlying case burden is substantially lower, but because many colorectal cancers may be present yet undetected until diagnosed at 50 years when screening is ultimately initiated. We are hoping this data can contribute to the earlier screening debates.
Another key point is that it is imperative that concerning symptoms (for example rectal bleeding) prompt a thorough, expedited work up and that patients are well aware of their cancer family histories as this may require much earlier screening (even before age 45 or 50).
MedicalResearch.com: What recommendations do you have for future research as a result of this work?
Response: A limitation of this study is its population-based design which limits the ability to determine exactly which patients had colorectal cancers detected at age 50 through screening versus diagnostic testing. Nevertheless, the significantly high rate of invasive cases supports that almost all cancers accounted for in the rate increase from age 49 to 50 would require aggressive treatment regardless of how they were detected. However, we feel that performing a more detailed analysis in a defined patient population to determine what proportion of colorectal cancer cases are diagnosed at 50 years through screening versus diagnostic testing will be important. Modeling studies that incorporate the steep incidence rates increase from age 49 to 50 can also be performed to try to estimate what the incidence rate increase would be at age 45 if earlier screening were initiated.
Any disclosures? Dr. Karlitz: Advisor for Exact Sciences. Consultant and Speakers Bureau for Myriad Genetics. Equity position in Gastro Girl and GI OnDemand.
Thank you for the invitation to interview.
Abualkhair WH, Zhou M, Ahnen D, Yu Q, Wu X, Karlitz JJ. Trends in Incidence of Early-Onset Colorectal Cancer in the United States Among Those Approaching Screening Age. JAMA Netw Open. 2020;3(1):e1920407. doi:10.1001/jamanetworkopen.2019.20407
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